The GS40 is a low maintenance, easy-to-use, and completely self-contained combustible gas leak detector designed to pinpoint gas leaks in the most demanding applications. An efficient and sensitive gas sensor is combined with solid-state circuitry which provides an audible alarm that increases in pitch as the concentration of the gas increases. An advanced semiconductor sensor and electronic control package enables detection of gases commonly found in service applications including: carbon monoxide, natural gas, propane, ammonia, methane, acetone, hydrogen, and iso-butane, with a virtually instantaneous alarm response period. Applications include the inspection of furnaces, valves, regulators, pipelines, meters, and other devices associated with combustible gas. A visual indication is also provided as well as provisions for an earphone for use in noisy environments. The GS40 is designed and manufactured in the USA with U.S. and globally-sourced components.